Interrelated power delivery controls – including engine control – Clutch control – Condition responsive control
Patent
1996-06-17
1998-04-14
Ta, Khoi Q.
Interrelated power delivery controls, including engine control
Clutch control
Condition responsive control
477 83, 477181, B60K 4102
Patent
active
057386099
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
This invention relates to a clutch control system for the automatic control of a motor vehicle clutch which connects an engine with a gearbox under the control of a driver-operated gear ratio selector member, the control system including an electronic control unit which controls initial clutch take-up on starting of the vehicle, clutch re-engagement following each ratio change, clutch disengagement on movement of the gear selector member to change the operative ratio of the gearbox, and clutch disengagement on the coming to rest of the vehicle, the level of clutch engagement being controlled in response to an engine speed error signal derived from a comparison of current engine speed and a reference speed signal generated by the control unit. Such a clutch control system is herein after referred to as a clutch control system of the kind specified.
BACKGROUND OF THE INVENTION
Examples of such systems are described in the applicants earlier European patents Nos. 0038113, 0043660, 0059035 and 0101220 and European Application No. 0566595.
Problems can arise with such systems when low speed manoeuvring is required, e.g. when parking or coupling up a trailer.
In particular, in such systems low speed manoeuvring necessitates the use of excessive engine speed since the clutch dues not normally begin to engage until the engine speed has been raised significantly above engine idle speed.
It is an object of the present invention to mitigate the above low speed manoeuvring problem.
SUMMARY OF THE INVENTION
Thus according to the present invention there is provided a clutch control system of the kind specified provided with sensing means to detect a "foot-off" condition of an engine controlling accelerator pedal and to provide an indication of the full range of movement of the accelerator pedal from the "foot-off" condition to the fully depressed position, the electronic control unit responding to an accelerator pedal "foot-off" signal to ensure that the reference speed signal is above the engine idle signal by a predetermined amount to prevent creeping of the associated vehicle due to partial clutch engagement at engine idle and being arranged on detection of a "foot-on" condition of the accelerator pedal to switch the reference speed signal to a level determined by accelerator pedal position, the reference speed signal being arranged to be close to engine idle speed at low levels of accelerator pedal depression so that the clutch will engage to a torque transmitting level thus allowing the vehicle to be manoeuvred at low engine speeds.
By switching the reference speed signal to a level close to idle speed at low levels of accelerator pedal depression, sufficient level of clutch engagement can be achieved at low engine speeds to enable the associated vehicle to be manoeuvred safely and without the need to raise the engine speed significantly above idle speed.
In practice the "foot-on" condition is set at a very small first predetermined level of depression of the accelerator pedal from the fully released position of the pedal.
The detection of the "foot-on" condition of the accelerator pedal may be accomplished by a sensor (e.g. a rotary potentiometer) which also provided the indication of the pedal position throughout the full range of movement of the pedal.
p Alternatively, a switch may be used to indicate the "foot-on" condition and another sensor (e.g. rotary potentiometer) used to measure the pedal depression throughout the remaining range of movement and the pedal.
The "foot-off" condition is set at a second predetermined level of depression of the accelerator pedal from the fully released condition which is smaller than the first level of depression to take into account the hysteresis of the pedal linkage etc. Thus as the accelerator pedal is released wren the pedal passes through this second predetermined level of depression as it approaches the fully released position the electronic control unit switches the reference speed signal to the predetermined amount above idle speed.
The foot
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Bowker Katharine Dianna
Jones Charles John
Willows Mark Stanley
Automotive Products plc
Germain Lee A.
Kwon Peter T.
Milliken Paul E.
Ta Khoi Q.
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